Green Party co-leaders say they reported MP Dr Elizabeth Kerekere to health authorities after they discovered she had breached pandemic restrictions.
In a statement on Tuesday afternoon, Kerekere said she had travelled from her home in Tairāwhiti to Wellington by plane despite being a household contact of a Covid-infected person.
She had been at Parliament yesterday. Consequently she has resigned her Covid-19 Response portfolio "with immediate effect" and apologised.
Green Party co-leader Marama Davidson said the co-leaders had expressed disappointment in Kerekere, and advised public health authorities of what had occurred.
"She has admitted and apologised for a mistake. We understand it's important for everyone, including MPs, to abide by the rules."
Today she resigned from her Covid-19 Response portfolio, and would not hold the Health portfolio nor sit on the Health Select Committee until further notice.
"I apologise profusely to my constituents, whānau, and colleagues for my mistake, and to everyone who is making huge sacrifices to follow rules that are designed to keep us all safe," Kerekere said.
"I am also sorry for adding to the risk and stress that our healthcare and essential workers on the front line continue to experience two years into a pandemic.
"As always, I acknowledge our Māori, Pasifika and community providers, who have worked tirelessly to support our hard-to-reach communities."
Davidson said MPs were not considered critical workers at this point so must isolate, rather than go to work with a daily RAT.
"It's very important that everyone upholds the rules, especially a Covid-19 spokesperson."
The co-leaders had acted as soon as they found out she was a close contact, Davidson said.
Davidson said Kerekere had offered to resign the Covid-19 portfolio, but caucus had subsequently decided she should also be removed from the health portfolios.
Kerekere is a first-term MP who last year led a record-breaking petition to ban conversion therapy, sparking the Government into action.
She was also a member of the Health and te pae oranga legislation select committees.
"I also want to acknowledge people who have underlying health conditions or are immunocompromised. I know you are also feeling the compounding effects of this pandemic and are making difficult individual choices every day to stay safe.
"I have discussed my mistake with the Green Party caucus and our co-leaders, and apologised to them also. I should have known better.
"The Green Party will continue to push for an equitable response to the Covid-19 pandemic and for Māori and Pasifika health providers to have the resources they need to keep their communities safe.
"I do not want my mistake to distract from this important kaupapa."
Prime Minister Jacinda Ardern said she was not aware of the full details of the situation, but said MPs should be held to a "high standard".
National Party leader Christopher Luxon said National had clear protocols for its MPs in place about the rules.